We agree with the recent letter by Woolderink et al. (1) that insulin glargine use during pregnancy may be appropriate. In contrast to that letter, which described the use of insulin glargine in pregnant women with type 1 diabetes, we detail the use of insulin glargine in four patients with gestational diabetes mellitus (GDM). Target blood glucose levels set by the American College of Obstetricians and Gynecologists for women with GDM include fasting glucose ≤95 mg/dl and 1-h postprandial glucose ≤130–140 mg/dl or 2-h postprandial glucose ≤120 mg/dl (2). These criteria are used by the Maternal-Fetal Medicine Clinic at Wake Forest University School of Medicine to determine the need for insulin.
The four women whose treatment we describe here were referred to our clinic and delivered between 1 December 2003 and 31 March 2005. The decision to initiate insulin glargine in these patients was based on postprandial self-monitored blood glucose readings <150 mg/dl. All four maintained blood glucose values that, on average, met the American College of Obstetricians and Gynecologists’ criteria for the remainder of their pregnancies using insulin glargine alone. Two of four patients had average fasting blood glucose values ≤95 mg/dl; the other two maintained average fasting blood glucose values ≤98 mg/dl. Their starting doses of insulin glargine ranged from 10 to 50 units, with an average of 29 units. Doses at delivery ranged from 18 to 78 units, with an average of 44 units.
For three patients with well-documented blood glucose values before initiating insulin glargine, the average reduction in fasting blood glucose was 15 mg/dl and the average postprandial decrease was 17 mg/dl. One patient experienced an average blood glucose reduction of 30 mg/dl, including reductions from 21 mg/dl after breakfast to 49 mg/dl after dinner.
All four women reported successful pregnancy outcomes. No infants were reported to have hypoglycemia, and one weighed >9 lb. One patient experienced hypoglycemic episodes using insulin glargine, with six episodes of blood glucose <60 mg/dl (53, 57, 54, 54, 59, and 58 mg/dl). She also reported skipping meals, especially breakfast. All six of her hypoglycemic episodes were in the time period labeled “2 h after breakfast.”
Starting doses of insulin glargine were implemented using half of the estimated total daily dose needed during that trimester. Total daily dose was calculated as 0.4–0.5 units/kg in the 1st trimester, 0.5–0.6 units/kg in the 2nd trimester, or 0.7–0.8 units/kg in the 3rd trimester. Insulin glargine was injected in the morning before breakfast and increased rapidly until blood glucose was at target. Throughout the rest of the pregnancy, insulin glargine doses were advanced by 3–5 units whenever readings reached the upper limit of the target range.
Morning dosing of insulin glargine contributed to target postprandial readings throughout the day, with no nocturnal hypoglycemia reported and without altering fasting glucose levels. Though the usual recommended starting dose of insulin glargine is 10 units, we found that higher starting doses were required to achieve blood glucose goals during pregnancy, especially in obese women.
Multiple studies (3–5) over many years have shown that tight glucose control during pregnancy is important to promote normal perinatal outcomes. Insulin glargine offers an alternative in GDM, especially for women with mild glucose intolerance. Additional research is needed to further elucidate the safety and effectiveness of using insulin glargine in women with GDM.
